The invention relates in general to an elevator control system and, in particular, to an actual position value transmitter for an elevator system.
In a typical elevator position control circuit, a pulse transmitter is coupled with a drive pulley, which can be driven by means of a cable attached to an elevator car and carried in friction contact over a guide roller, and generates a pulsed signal to a car distance counter. An output of the distance counter is connected as a feedback signal with an input of a control device of the position control circuit.
In the European Patent Application No. 0 026 406, a drive control for an elevator is shown which includes a typical actual position value transmitter. Herein the pulse transmitter is coupled with the shaft of the speed-limiting device and is driven by an endless rope guided over a drive pulley attached to the elevator car and which is tightened by a tension roller with a weight in the shaft pit. This drive control is designed in microcomputer technology and exhibits a floor level memory in the form of a write-read memory in which floor level values assigned to the floor numbers are referred to a certain base. The floor levels are required for the shop initiation and the precise entrance of the elevator at a floor.
The writing-in of the floor levels into the floor level memory takes place during an instructional travel prior to the first putting in operation of the elevator. The instructional travel starts at the lowest floor in the upward direction and, at each floor, the instantaneous counter reading of the car distance counter is transferred as the floor level value into the floor level memory.
The rope drive of the speed limiting device exhibits slip, which can be recognized in such a manner, that the counter readings transferred during the upward travel are smaller than the actual level numbers of the respective floors. These discrepancies have no effect in all later upward travel, since the counter read-outs and floor levels agree precisely. During downward travel, slip also appears, which acts in such a way that the counter read-outs of the car distance counter are greater than the actual level numbers of the respective floors. Since in the downward travels the levels which were stored during the upward-instructional travel are used, a stopping inaccuracy can occur at the stop of the elevator car after a downward travel, which inaccuracy corresponds to the sum of the slip of the upward and downward travel.